Effects of Acrylic Restorations on the Periodontium of Monkeys

Effects of Acrylic Restorations on the Periodontium of Monkeys CARLOS E. NASJLETI, WALTER A. CASTELLI, and BENJAMIN E. KELLER Veterans Administration Hospital and the University of Michigan, Ann Arbor, Michigan 48105, USA Replanted teeth that had an acrylic restora- implanted acrylic teeth. Similar results tion in the middle third of their roots were were obtained by Tobin-White,9 who placed studied from three days to six months after acrylic teeth into sockets in which fluid grafting. The study revealed that the acrylic acrylic resin had been introduced before po- obturator elicited epithelial proliferation, sitioning the implants. These conflicting re- fibrous encapsulation, moderate chronic in- ports indicated a necessity for further flammation, and adjacent alveolar bone loss. investigation. We thought that the histo- pathologic condition of the periodontium in Data dealing with successful or unsuccessful relation to the acrylic restoration must be acrylic tooth implants have accumulated delineated clearly. gradually during the past 20 years. Flohr' The present study is a histological exam- studied plastic material as a possible sub- ination of the periodontium of replanted stitute for natural teeth by placing screw-type teeth that had an acrylic restoration in the acrylic roots into surgically created alveolar middle third of their roots. The study was sockets. He reported that normal connective done from three days to six months after tissue formed against the acrylic, and only grafting. With this model, observations of minimal infiltration occurred. Hodosh, et the periodontal tissue reaction around ce- al24 reported a high degree of success with mentum and the acrylic restoration could be acrylic implants in man, baboons, and dogs. compared. Success was measured by the firmness and stability of the implants, by their ability to Materials and Methods stand up under the stress of mastication, and Nine healthy male rhesus monkeys by the absence of gross gingival and perio- (Macaca mulatta) were used for this study. dontal diseases. Brown, Neff, and Tylenda5 All the monkeys were adults and were ap- reported encouraging results in a preliminary proximately the same size and weight. A step study of acrylic tooth implants in monkeys. by step sequence of the methods used was On the other hand, Waerhaug and Zander6 reported recently.10 Briefly, after extraction, demonstrated that acrylic resin implants ex- the left central maxillary incisors were erted little or no irritation on hard and soft treated endodontically with zinc oxide- tissues, but concluded that the life of the eugenol paste and gutta-percha points, and acrylic implant is limited and that it is prob- a cavity was prepared in the distal aspect ably of no practical value. Narang and of the middle third of the roots. The pre- Wells7 reported that efforts to achieve long- pared cavity was filled with a cold-curing term maintenance of acrylic tooth implants acrylic resin* and after four minutes setting have achieved only limited success. Failures time, the tooth was replanted. For stabiliza- were characterized by gingival inflammation, tion, the replants were sprinted by cementing alveolar bone loss, and excessive mobility of a common metal inlay into previously pre- the acrylic tooth implants. In spite of careful pared cavities of the central incisors. After splinting, Iwaschenko8 found epithelial pro- surgery, the monkeys were given 100 mg liferation and subsequent exfoliation of the * Sevriton, Amalgamated Dental Trade Dist., Ltd., Received for publication June 24, 1971. London, Eng. 1382 I'ol .5 No}. 5 ACRYL[IC RFS7 ORATIONS & THE IPERIODONTIUM 1383 FIG 1. Twenty one days after tooth replantation. Dense band of transseptal periodontal fibers extends from cernentum of replanted tooth (re) to cementLum of control untreated tooth (co) over crest of alveolar bone septum (HL&E stain; orig mag X45, reproduced at 78%). oxytetracycline dissolved in 16 ounces of ment and the intense leukocytic infiltration, water daily and were maintained on a soft the original connective tissue outline was diet for the first week. The monkeys were preserved without noticeable sloughing. By killed postoperatively at 3, 6, 21, and 30 six days, the crevicu~lar epithelium was re- days, and at three, four, and six months. The attached at the cementoenamel junction, and involved teeth with surrounding bone and further repair was observed by proliferation soft tissue were excised in block sections. of epithelial cells, which quantitatively re- These sections were fixed in 10% buffered stored the thickness of the tissue in that Formalin solution, and were decalcified in region. The blood clot in this specimen was either formic or nitric acid. Acrylic restora- replaced partially by loose fibrillar tissue, tions were dissolved in chloroform for four and at the periphery of the clot there was hours. Serial sections of the decalcified, evidence of vascular proliferation. Lympho- paraffin-embedded tissues were sectioned in cytic and histocytic inflammatory cells be- the mesial-distal direction, and stained with came prominent along the replanted root. hematoxylin and eosin (H&E) and Mal- The collagen fibers of the periodontal mem- lory's periodic acid-Schiff (PAS) stain, for brane demonstrated increased cellularity, histological examination. and a definite tendency toward orientation. In the middle third of the root, adjacent Results to the acrylic obturator, a trace of a thin Histological sections of the three day post- zone of parallel collagen fibers with inter- operative specimen disclosed a broad zone of spersed leukocytes was seen. Between this fibrin clot, which was undergoing organiza- zone and the interdental septum of the tion. Despite the lack of epithelial reattach- alveolar bone, the connective tissue seemed slightly edematous and periodontal fibers ap- * Cosa Terramycin, Pfizer & Co., Inc., New York, peared somewhat disoriented. Healing in the NY. 21-day specimen was advanced considerably 1384 NASJLETI, CASTE! LI, AND KElLER I Dent Res Septeinher-October .1972 over that observed in the six-(lay specimen. The subgingival connective tissue was in- filtrated moderately with chronic inflammatory cells, and a dense band of transseptal periodontal fibers extended from the cemen- turn of one incisor to the cementum of the adjacent incisor over the crest of the interdental septum of alveolar bone (Fig 1). At the acrylic site there was a notable zone of moderate round cell infiltration, fibrosis, and fatty tissue, as well as hyalin, degeneration. Coarse connective tissue fibers were aligned parallel to the acrylic cavity. When the apical portion of the root was scanned, fibroblastic and osteoblastic activity was evident, and cemental resorption and dentoalveolar ankylosis were a common finding. FIG 3.- Area between cervical third and acrylic third of root of a 30-day specimen. Note fibrous components of encapsulated zone attaching to root cement-lum. re, Replanted tooth; e, epithelial proliferation (H&E stain; orig mag x250, reproduced at 56%). Three specimens were available for a 30- day postoperative evaluation. In every in- stance, the cervical third of the root showed a decrease in the cellularity of the periodontal membrane. Occasionally, epithelial rests of Malassez and pools of fibrillar material without definite arrangements were noted. In all three specimens, tissue elements adjacent to the acrylic cavity showed the following features: (1) An epithelial proliferation extended over the whole acrylic wall (Fig 2); however, this epithelial proliferation was not connected with the crevicu- lar epithelium. This epithelial proliferation appeared to form a protective barrier between the acrylic obturator and the adjacent FIG 2.-Acrylic site of a 30-day replanted tooth. Polymer elicited epithelial proliferation connective tissue fibers. (2) In the perio- (e), fibrous encapsulation (c), and chronic dontal space and covering the epithelial pro- inflammation (ch) (H&E stain; orig mag X250, liferation, the acrylic restoration also elicited reproduced at 67%). the formation of a fibrous encapsulation. Vol 51 No. 5 ACRYLIC RESTORATIONS & THE PERIODONTIUM 1385 The fibers forming this encapsulated zone dontal membrane to become reestablished were parallel to the epithelial proliferation as after replantation. In their work, dento- well as to the acrylic cavity, which denotes alveolar ankylosis was not observed; and, a nonfunctional orientation. The fibrous without exception, connective tissue filled components of the encapsulated zone were the space between the transplanted root and attached to the cementum root surface (Fig the alveolar bone. 3). (3) A chronic inflammatory reaction In the present study half of the tooth re- was present in the epithelial proliferation plants showed dentoalveolar ankylosis, layer and in the fibrous encapsulation layer. whereas the other half did not show dento- There was a moderate number of foreign alveolar ankylosis. The cause for these differ- body cells, macrophages, lymphocytes, and ent responses could not be determined. In polymorphonuclear leucocytes (Fig 2). (4) the present study, such factors as exodontia, A notable decrease in osteoblastic activity at as well as overmanipulation during root the mesial margins of the interdental sep- canal therapy and acrylic cavity preparation, tums and a somewhat granular appearance may account for the response of the teeth of the bone was observed. In addition, the that resulted in dentoalveolar ankylosis.

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